[Discuss-gnuradio] Stream tags

[Patrik Eliardsson]

Hi,

I've tried the new stream tags and like them, but when I've a block in my 
flowgraph that change the stream rate I'm not sure how the absolute sample 
number is calculated.

Consider the flowgraph below where B0, B1 and B4 are gr_sync_block and B2 is a 
gr_block that increases the stream rate in the flowgraph.
B0 -> B1 -> B2 -> B4

If I set tags on sample 0 and 200 in block B0 and check the tags in block B1 
everything is correct, I find them at sample 0 and 200. But if I check the tags 
in block B4 I find them at 0 and 400 while I expected to find them on 0 at 527. 
The B2 block consumes 200 samples and produces 527 samples, this is a rate of 
2.635 and the tag absolute sample number is increased by a ratio of 2. How is 
the absolute sample number calculated?

I found that it is possible to change the policy of how the tags propagate 
between blocks. My default setting was TPP_ALL_TO_ALL. When I changed it to 
TPP_ONE_TO_ONE I got the following error "gr_block_executor: propagation_policy 
'ONE_TO_ONE' requires ninputs == noutputs", I tested it on the flowgraph above. 
With the TPP_ONE_TO_ONE policy, shouldn't the tags only propagate from B0 to B1?


BR,
Patrik Eliardsson